Thermal separators are pieces of apparatus which operate on pulsed gas flows and take advantage of the physical phenomena which result from this in order to subdivide an initial compressed gas flow at a certain temperature into a first flow of lower temperature and a second flow of higher temperature, the latter flow possibly being low or zero, so that the systems behave in effect like gas-cooling apparatuses. Apparatuses of this type are well known to those working in this field and reference could be made, in this respect, to Marchal et al., U.S. Pat. No. 3,541,801, Marchal et al., U.S. Pat. No. 3,653,225 and Boy-Marcotte et al., U.S. Pat. No. 3,828,574, which describe various embodiments of such apparatuses in which the pulsed flows in question are obtained starting from a continuous supply of gas, using an injector-distributor which may either be static and in this case include a fluid bistable, or be movable in rotation or linear motion and in this case include a type of rotating plug body or sliding valve, depending on the case.
The present invention is directed more in particular to apparatuses of this last type, in other words of the type using a movable injector-distributor, which are particularly, although not exclusively, adapted to treat small gas flows.
In thermal separators which are known at present, which operate using a rotary injector and usually run under conditions of appreciable flow, the gas under high pressure is injected radially, from the center towards the periphery, into a bundle of receiving tubes which are arranged to radiate on a crown formation or are mounted in a star configuration.
If it is desired to provide a scaled-down apparatus for operating under low flow conditions, the injector will be small and consequently the leakage from the injector will be correct, but the receiver tubes will of necessity have a very small diameter, which is a difficult thing to provide in practice and has a harmful effect on the yield (as a result of fluid friction) unless it is rotating fast. Moreover, the permanent leakage at the point of entry to the rotating injector is appreciable.
Moreover, it is difficult, for reasons of geometry, to connect together two diametrically opposing tubes on the crown, into one single one, for increasing the diameter of them in the working region.
If, furthermore, only several large tubes are placed on the crown, the leakage will increase (since the injector must then be larger) and it is necessary to operate at very high speeds of rotation, in order to operate correctly.
It will thus be seen that the thermal separators of the rotary type at present in use are barely suitable for the treatment of small flows where the requirements: correct speed of opening, use of tubes which are not too small and, above all, negligible leakage, are more difficult to achieve.